001/** 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017package org.apache.camel.processor; 018 019import java.util.Iterator; 020import java.util.List; 021 022import org.apache.camel.AsyncCallback; 023import org.apache.camel.Exchange; 024import org.apache.camel.Predicate; 025import org.apache.camel.Processor; 026import org.apache.camel.Traceable; 027import org.apache.camel.util.ExchangeHelper; 028import org.apache.camel.util.ObjectHelper; 029import org.slf4j.Logger; 030import org.slf4j.LoggerFactory; 031 032/** 033 * A processor which catches exceptions. 034 * 035 * @version 036 */ 037public class CatchProcessor extends DelegateAsyncProcessor implements Traceable { 038 private static final Logger LOG = LoggerFactory.getLogger(CatchProcessor.class); 039 040 private final List<Class<? extends Throwable>> exceptions; 041 private final Predicate onWhen; 042 private final Predicate handled; 043 044 public CatchProcessor(List<Class<? extends Throwable>> exceptions, Processor processor, Predicate onWhen, Predicate handled) { 045 super(processor); 046 this.exceptions = exceptions; 047 this.onWhen = onWhen; 048 this.handled = handled; 049 } 050 051 @Override 052 public String toString() { 053 return "Catch[" + exceptions + " -> " + getProcessor() + "]"; 054 } 055 056 public String getTraceLabel() { 057 return "catch"; 058 } 059 060 @Override 061 public boolean process(final Exchange exchange, final AsyncCallback callback) { 062 Exception e = exchange.getException(); 063 Throwable caught = catches(exchange, e); 064 // If a previous catch clause handled the exception or if this clause does not match, exit 065 if (exchange.getProperty(Exchange.EXCEPTION_HANDLED) != null || caught == null) { 066 callback.done(true); 067 return true; 068 } 069 if (LOG.isTraceEnabled()) { 070 LOG.trace("This CatchProcessor catches the exception: {} caused by: {}", caught.getClass().getName(), e.getMessage()); 071 } 072 073 // store the last to endpoint as the failure endpoint 074 if (exchange.getProperty(Exchange.FAILURE_ENDPOINT) == null) { 075 exchange.setProperty(Exchange.FAILURE_ENDPOINT, exchange.getProperty(Exchange.TO_ENDPOINT)); 076 } 077 // give the rest of the pipeline another chance 078 exchange.setProperty(Exchange.EXCEPTION_HANDLED, true); 079 exchange.setProperty(Exchange.EXCEPTION_CAUGHT, e); 080 exchange.setException(null); 081 // and we should not be regarded as exhausted as we are in a try .. catch block 082 exchange.removeProperty(Exchange.REDELIVERY_EXHAUSTED); 083 084 // is the exception handled by the catch clause 085 final boolean handled = handles(exchange); 086 087 if (LOG.isDebugEnabled()) { 088 LOG.debug("The exception is handled: {} for the exception: {} caused by: {}", 089 new Object[]{handled, e.getClass().getName(), e.getMessage()}); 090 } 091 092 boolean sync = processor.process(exchange, new AsyncCallback() { 093 public void done(boolean doneSync) { 094 if (!handled) { 095 if (exchange.getException() == null) { 096 exchange.setException(exchange.getProperty(Exchange.EXCEPTION_CAUGHT, Exception.class)); 097 } 098 } 099 // always clear redelivery exhausted in a catch clause 100 exchange.removeProperty(Exchange.REDELIVERY_EXHAUSTED); 101 102 if (!doneSync) { 103 // signal callback to continue routing async 104 ExchangeHelper.prepareOutToIn(exchange); 105 } 106 107 callback.done(doneSync); 108 } 109 }); 110 111 return sync; 112 } 113 114 /** 115 * Returns with the exception that is caught by this processor. 116 * 117 * This method traverses exception causes, so sometimes the exception 118 * returned from this method might be one of causes of the parameter 119 * passed. 120 * 121 * @param exchange the current exchange 122 * @param exception the thrown exception 123 * @return Throwable that this processor catches. <tt>null</tt> if nothing matches. 124 */ 125 protected Throwable catches(Exchange exchange, Throwable exception) { 126 // use the exception iterator to walk the caused by hierarchy 127 Iterator<Throwable> it = ObjectHelper.createExceptionIterator(exception); 128 while (it.hasNext()) { 129 Throwable e = it.next(); 130 // see if we catch this type 131 for (Class<?> type : exceptions) { 132 if (type.isInstance(e) && matchesWhen(exchange)) { 133 return e; 134 } 135 } 136 } 137 138 // not found 139 return null; 140 } 141 142 /** 143 * Whether this catch processor handles the exception it have caught 144 * 145 * @param exchange the current exchange 146 * @return <tt>true</tt> if this processor handles it, <tt>false</tt> otherwise. 147 */ 148 protected boolean handles(Exchange exchange) { 149 if (handled == null) { 150 // handle by default 151 return true; 152 } 153 154 return handled.matches(exchange); 155 } 156 157 public List<Class<? extends Throwable>> getExceptions() { 158 return exceptions; 159 } 160 161 /** 162 * Strategy method for matching the exception type with the current exchange. 163 * <p/> 164 * This default implementation will match as: 165 * <ul> 166 * <li>Always true if no when predicate on the exception type 167 * <li>Otherwise the when predicate is matches against the current exchange 168 * </ul> 169 * 170 * @param exchange the current {@link org.apache.camel.Exchange} 171 * @return <tt>true</tt> if matched, <tt>false</tt> otherwise. 172 */ 173 protected boolean matchesWhen(Exchange exchange) { 174 if (onWhen == null) { 175 // if no predicate then it's always a match 176 return true; 177 } 178 return onWhen.matches(exchange); 179 } 180}